Trends in lung cancer incidence and mortality have followed trends in tobacco use, as cigarette smoking is estimated to cause approximately 90 percent of lung cancer deaths in men and 80 percent in women. However, exposure to radon-an odorless radioactive gas that can become trapped in homes-is considered the second leading cause of lung cancer. A very important aspect of the relationship between radon and lung cancer is the strong interaction between radon exposure and smoking in lung cancer risk. The EPA estimates that 86 percent of radon-related lung cancer deaths are in ever-smokers. As such, the vast majority of the public health burden of radon is among smokers and former smokers. The overall goal of our proposed research is to elucidate the potential impact and costs of a selected set of public policies aimed at reducing the burden of radon-induced lung cancer in the U.S., taking into account the strong interaction between radon exposure and smoking, and the fact that we are currently in an era of decreased smoking. Our specific aims are as follows: 1) to modify an existing population-based dynamic model that predicts tobacco use, radon exposure, and lung cancer mortality by incorporating revised structure and parameters from the National Academy of Sciences' Biological Effects of Ionizing Radiation VI model; 2) to use the modified model to estimate the impact that radon had on lung cancer mortality during the time period of 1980-2005, taking into account decreases in smoking among adults over this time; 3) to use the modified radon model to conduct a variety of policy simulation exercises regarding both radon testing/remediation and tobacco control (including the targeting of radon education/testing/remediation at smokers); and 4) to conduct cost-effectiveness analyses of a selected set of policy approaches to reducing lung cancer mortality, comparing policy strategies focused on smoking cessation and those focused on reducing exposure to radon. Our work seeks to add clarity to a number of questions that are central to sound public policy regarding radon but have yet to be elucidated. At the center of our proposed research is the need for policy research and discourse to better explicate the implications of the interaction between radon exposure and smoking for lung cancer. In sum, our work will help to elucidate the relative impact and cost-effectiveness of residential radon remediation strategies versus smoking reductions on radon-related lung cancer in the 21st century. [unreadable] [unreadable] [unreadable] [unreadable]